High-Temperature Oxidation Resistant Nanocoatings on Austenitic Stainless Steels.
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Mater. Res. Soc. Symp. Proc. Vol. 1243 © 2010 Materials Research Society
High-Temperature Oxidation Resistant Nanocoatings on Austenitic Stainless Steels. Hugo F. Lopez Materials Department University of Wisconsin-Milwaukee P.O. Box 784, Milwaukee WI 53209 ABSTRACT In recent years, the increasing energy costs have lead to power utility industries to seek/develop high efficiency systems of production and of energy utilization. In addition, environmental concerns regarding greenhouse gas emissions are playing a major role in the development of clean energy systems. The development of metallic materials that can withstand elevated temperatures is among the viable alternatives to increase energy efficiency. Nevertheless, for this to happen, the corrosion and oxidation resistance of Fe- and Ni-based alloys needs to be significantly improved. Among the possible ways to enhance the life of high temperature alloys is the application of protective ceramic coatings. Conventional coatings are expensive and the protective effects controversial at times. An alternative which offers a great potential is the application of nano-ceramic coatings. Hence, in this work nanocrystalline coatings based on nano-CeO2 are applied to an austenitic stainless steel 304L and then exposed to elevated temperatures. Weight changes are monitored as a function of time and the results are compared with uncoated alloys tested under similar conditions. In addition, computer simulations of possible rate limiting diffusion mechanisms are carried out. It is found that the nanocoatings provided remarkable high-temperature oxidation resistance and improved scale adhesion. In particular, it is found that the smaller the nanoparticles are, the more effective the nanocoatings in providing oxidation resistance. INTRODUCTION Environmental concerns related to the greenhouse gas emissions and to the energy crisis and costs have been forcing power utility industries into improving the efficiency of energy production. Among the viable alternatives to increase energy efficiency is the likelihood of safe operation at elevated temperatures. However, for this to take place it is necessary to improve the corrosion and oxidation resistance of high temperature Fe- and Ni-based alloys. These alloys can be used under extreme temperatures and environments through the use of surface coatings. Typically, the development of protective Cr2O3, Al2O3 and rare-earth-oxide scales prevents/reduces the high-temperature degradation of the alloy substrates. However, at elevated temperatures beyond 800oC the oxide scales developed are not able to provide the desired protection. Hence high temperature resistant coatings are employed [1-6]. Yet, a number of the available coatings are expensive and do not provide the desired protection. In recent years, the use of nano-structured materials in a wide variety of applications has attracted significant attention due to their unique physical and chemical properties. Among these applications, the use of nanocoatings for corrosion and high temper
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